DESCRIPTION: (adapted in part from the abstract) The objective of this project is to understand the mechanisms that underlie the vocal communication and behavior of free-ranging baboons (Papio cynocephalus ursinus). The first aim is to characterize the information content of alarm calls and determine their function in baboon society. Baboon alarm calls appear to be adapted for long-range communication, occur in different contexts, and evoke qualitatively different responses in the recipient. From an evolutionary perspective, the existence of these factors favors the development of discrete, acoustically distinct call types such as has been identified in vervet monkeys. However, baboon alarm calls resemble human speech in that they are graded rather than discrete. Experimentally controlled recordings of these alarm calls will be played back to individuals in specific contexts to examine the functional significance of these calls and to determine if the listeners perceive these calls as distinct signals. The second aim is to examine baboons' perception of their own and other individuals' social relationships, concentrating on recognition of each other's relative dominance ranks. As in the first aim, experimentally controlled playbacks will be used. This technology permits the investigator to create anomalous or consistent dominance interactions and to monitor baboon reactions.